Betamethasone is a potent corticosteroid steroid with anti-inflammatory and immunosuppressive properties. Unlike other drugs with these effects, betamethasone does not cause water retention. It is generally applied as a topical cream, ointment, foam, lotion or gel to treat itching. Betamethasone sodium phosphate has been prescribed as an intramuscular injection (IM) for itching from various ailments, including allergic reactions to poison ivy and similar plants, and to treat arthritis and other joint related diseases.
Currently, the delivery modes consist of systemic delivery or repeated intra-articular injections. These are fraught with serious complications. Direct intra-articular injection allows the use of compounds with low or no oral bioavailability. However, even then, the synovial membrane is a large and efficient resorptive surface, and highly soluble drugs are cleared rapidly, requiring frequent reinjections. It would therefore be beneficial to formulate a sustained release injection that has the potential to maintain a therapeutic drug level within the joint space over a period of several weeks to several months, decreasing the number of injections and injection-related side effects.